Switching power supply circuit for improving load capacity of non-control output circuit

Abstract

The utility model discloses a switching power supply circuit capable of improving load capacity of a non-control output circuit. The circuit structure comprises an AC input circuit, an EMI rectification filter circuit, a power transformer circuit, a PWM control output circuit, a non-control output circuit, a PWM regulation control circuit and a load switching circuit. According to the switching power supply circuit, the load switching circuit is designed, so that the whole switching power supply not only can meet the requirements of no-load power consumption and energy efficiency, but also can meet the stable output of a non-control output circuit when a PWM control output circuit is in a no-load state, and the switching power supply circuit has very strong load capacity; the problem that the voltage of a non-PWM control output circuit cannot be adjusted due to the fact that a feedback mechanism has problems in multi-path output is solved, and the on-load function and practicability of the multi-path output switching power supply are enhanced. And the whole circuit structure is simple in design, and the manufacturing cost can be reduced.

Description

Technical Field

[0001] This utility model belongs to the field of switching power supply technology, specifically relating to a switching power supply circuit that improves the load-carrying capacity of non-control output circuits. Background Technology

[0002] In a multi-output switching power supply, only one output participates in the primary PWM control, while the others do not. Due to no-load power consumption requirements, dummy loads cannot be applied to the outputs. Therefore, when the output participating in primary PWM control is unloaded while the others are loaded, its output voltage will drop below specifications. This is because multi-output switching power supplies typically only regulate the main output, and the PWM controller can only accept one feedback signal. If the other outputs are not controlled, their voltage regulation depends on the load condition of the main output. When the main output is unloaded while the other outputs are loaded, the main output may not provide sufficient feedback, leading to voltage instability in the other outputs. Therefore, the problem with multi-output power supplies is that the feedback mechanism of the main output cannot adjust the voltage of other output circuits. However, multi-output switching power supplies can replace multiple single-output power supplies with a single power supply, reducing material costs and installation complexity. Therefore, it is necessary to design multi-output switching power supplies that can also carry loads even without control output circuits. Utility Model Content

[0003] The purpose of this invention is to address the above-mentioned problems by providing a switching power supply circuit that improves the load-carrying capacity of the non-control output circuit, enabling the non-control output circuit of a multi-output switching power supply to also carry a load, thereby enhancing the functionality and practicality of the multi-output switching power supply.

[0004] This utility model is achieved through the following technical solution:

[0005] A switching power supply circuit for improving the load-carrying capacity of the non-controlled output circuit is characterized by the following: its circuit structure includes an AC input circuit, an EMI rectifier and filter circuit, a power transformer circuit, a PWM control output circuit, a non-controlled output circuit, a PWM adjustment and control circuit, and a load switching circuit.

[0006] The output terminal of the AC input circuit is connected to the EMI rectifier and filter circuit. The positive terminal of the output terminal of the EMI rectifier and filter circuit is connected to the positive terminal of the first winding of the primary side of the power transformer T1 in the power transformer circuit. The negative terminal of the first winding of the primary side is connected to the PWM regulation and control circuit. The second winding of the primary side of the power transformer T1 provides the operating voltage to the PWM control chip U1 of the PWM regulation and control circuit. The output of the first secondary winding of the power transformer T1 in the power transformer circuit is connected to the PWM control output circuit, and the output of the second secondary winding of the power transformer T1 is connected to the non-control output circuit. The output of the PWM control output circuit inputs a feedback signal to the feedback input terminal of the PWM control chip U1 in the PWM adjustment control circuit through the optocoupler chip U4. The non-control output circuit includes a step-down voltage regulator chip U3, the voltage input terminal of which is connected to the output terminal of the second secondary winding of the power transformer T1. The load switching circuit is connected between the PWM control output circuit and the non-control output circuit. The load switching circuit includes transistors Q2, Q3, and Q4, an optocoupler chip U5, and Zener diodes Z1 and Z2. The voltage input terminal of the chip U3 in the non-control output circuit is connected to the base of transistor Q2 through the series Zener diodes Z1 and Z2 and resistor R38, and the collector of transistor Q2 is connected to the non-control output circuit through resistor R32. The positive output terminal Vo2 of the circuit is connected to the signal ground SGND2 of the non-control output circuit. The collector of transistor Q2 is connected to the base of transistor Q4 via diode D1. The emitter of transistor Q4 is connected to signal ground SGND2. The collector of transistor Q4 is connected to one input terminal of optocoupler chip U5. The other input terminal of optocoupler chip U5 is connected to the positive output terminal Vo2 via resistor R29. One output terminal of optocoupler chip U5 is connected to resistor R... 27 is connected to the positive output terminal Vo1 of the PWM control output circuit. The other output terminal of the optocoupler chip U5 is connected to the base of transistor Q3. The emitter of transistor Q3 is connected to the signal ground SGND1 of the PWM control output circuit. A load resistor R21, R23, R25, and R19 are connected in parallel between the collector of transistor Q3 and the positive output terminal Vo1. When neither the PWM control output circuit nor the non-control output circuit is connected to a load, the Zener diodes Z1 and Z2 are reverse-biased and broken down.

[0007] Furthermore, the AC input circuit is equipped with an overcurrent protection fuse F1 and a lightning protection varistor MOV1.

[0008] Furthermore, the buck regulator chip U3 is model number PL82051.

[0009] Furthermore, the optocoupler chips U4 and U5 are model number EL1019.

[0010] Furthermore, the transistors Q2, Q3, and Q4 are 2222 type transistors.

[0011] The beneficial effects of this utility model are as follows: The switching power supply circuit of this utility model, which improves the load-carrying capacity of the non-control output circuit, is designed with a load switching circuit, so that the entire switching power supply can not only meet the no-load power consumption efficiency requirements, but also meet the stable output of the non-control output circuit when the PWM control output circuit is no-load, and has a strong load-carrying capacity; it solves the problem that the voltage of the non-PWM control output circuit cannot be adjusted due to the problem of feedback mechanism in multi-output circuits, and enhances the load-carrying function and practicality of multi-output switching power supplies; and the entire circuit structure design is simple, which can also reduce manufacturing costs. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the principle of this utility model.

[0013] Figure 2 This is the circuit schematic diagram of this utility model.

[0014] Figure 3 for Figure 2 A magnified view of a portion of the image.

[0015] In the diagram, 1 is the AC input circuit, 2 is the EMI rectifier and filter circuit, 3 is the power transformer circuit, 4 is the PWM control output circuit, 5 is the non-control output circuit, 6 is the PWM adjustment and control circuit, and 7 is the load switching circuit. Detailed Implementation

[0016] The present invention will be further illustrated below with reference to specific examples and accompanying drawings.

[0017] like Figures 1-3 As shown, a switching power supply circuit for improving the load-carrying capacity of the non-controlled output circuit includes an AC input circuit 1, an EMI rectifier and filter circuit 2, a power transformer circuit 3, a PWM control output circuit 4, a non-controlled output circuit 5, a PWM regulation and control circuit 6, and a load switching circuit 7.

[0018] The AC input circuit 1 is equipped with an overcurrent protection fuse F1 and a lightning protection varistor MOV1. The output terminal of the AC input circuit 1 is connected to the EMI rectifier and filter circuit 2. The positive terminal of the output terminal of the EMI rectifier and filter circuit 2 is connected to the positive terminal of the first primary winding of the power transformer T1 in the power transformer circuit 3. The negative terminal of the first primary winding is connected to the drain of the MOSFET Q1 in the PWM regulation and control circuit 6. The gate of the MOSFET Q1 is connected to the control output pin of the PWM control chip U1 (model KP201E). The source of the MOSFET Q1 is connected to PGND through a resistor R7. The second primary winding of the power transformer T1 provides the operating voltage to the chip U1. The positive terminal of the second primary winding is connected to the VDD pin of the chip U1 through a diode D7, a resistor R9, and a diode D3.The output of the first secondary winding of the power transformer T1 in the power transformer circuit 3 is connected to the PWM control output circuit 4, and the output of the second secondary winding of the power transformer T1 is connected to the non-control output circuit 5. The output of the PWM control output circuit 4 inputs a feedback signal to the feedback input terminal FB of the PWM control chip U1 in the PWM adjustment and control circuit 6 through the optocoupler chip U4. The non-control output circuit 5 includes a step-down voltage regulator chip U3, model PL82051, and the voltage input of chip U3 is... The input terminal is connected to the output terminal of the second secondary winding of the power transformer T1; the load switching circuit 7 is connected between the PWM control output circuit 4 and the non-control output circuit 5; the load switching circuit 7 includes transistors Q2, Q3, and Q4, an optocoupler chip U5, and Zener diodes Z1 and Z2; transistors Q2, Q3, and Q4 are 2222 type transistors; the voltage input terminal of chip U3 in the non-control output circuit 5 is connected to the base of transistor Q2 through series Zener diodes Z1 and Z2 and resistor R38. One path of the collector of transistor Q2 is connected to the positive output terminal Vo2 of the non-controlled output circuit 5 through resistor R32. The emitter of transistor Q2 is connected to the signal ground SGND2 of the non-controlled output circuit 5. The other path of the collector of transistor Q2 is connected to the base of transistor Q4 through diode D1. The emitter of transistor Q4 is connected to the signal ground SGND2. The collector of transistor Q4 is connected to one input terminal of optocoupler chip U5. The other input terminal of optocoupler chip U5 is connected to the positive output terminal Vo2 through resistor R29. One output terminal of U5 is connected to the positive output terminal Vo1 of the PWM control output circuit 4 through resistor R27. The other output terminal of optocoupler chip U5 is connected to the base of transistor Q3. The emitter of transistor Q3 is connected to the signal ground SGND1 of the PWM control output circuit 4. Load resistors R21, R23, R25, and R19 are connected between the collector of transistor Q3 and the positive output terminal Vo1. When neither the PWM control output circuit 4 nor the non-control output circuit 5 is connected to a load, Zener diodes Z1 and Z2 are reverse-biased and broken down.

[0019] The optocoupler chips U4 and U5 are model number EL1019.

[0020] Existing multi-output switching power supplies typically only regulate the main output voltage because the PWM controller can only accept one feedback signal. If other circuits are not involved in control, their voltage regulation depends on the load condition of the main output. When the main output is unloaded while other circuits are loaded, the main circuit may not be able to provide sufficient feedback, leading to voltage instability in the other circuits. Furthermore, when the main circuit is unloaded, the PWM controller may reduce the duty cycle to reduce energy transfer, but at this time, other circuits need energy, but due to the lack of independent feedback, they cannot adjust their duty cycles, causing their voltages to drop. Simultaneously, because a dummy load cannot be applied, the main circuit cannot maintain sufficient voltage under light load or no-load conditions, further affecting other circuits. These factors collectively cause the voltage of other non-controlled output circuits to exceed specifications under specific load conditions. The circuit design of this invention adds a load switching circuit 7 between the PWM control output circuit 4 and the non-control output circuit 5, which can meet both the no-load power consumption efficiency requirements and the stable output of the non-control output circuit 5 when the PWM control output circuit 4 is unloaded, providing strong load-carrying capacity.

[0021] Its working principle is as follows: Figure 2 , Figure 3 The feedback signal of the PWM control output circuit 4 is transmitted to U1 through U4 to participate in the PWM regulation. The output of the non-control output circuit 5 does not participate in the PWM control. When neither output is under load, the Zener diodes Z1 and Z2 are broken down, thereby turning on transistor Q2 and turning off transistors Q4 and Q3. The parallel load resistors R21, R23, R25, and R19 do not act as loads at this time. Since the resistance value of resistor R32 (10KΩ) is set very large, the no-load power consumption of the power supply is very low at this time, meeting the energy efficiency requirements. When the PWM control output circuit 4 is unloaded and the non-control output circuit 5 is loaded, the voltage input terminal V1 of the chip U3 of the non-control output circuit 5 will drop first. At this time, the Zener diodes Z1 and Z2 will not break down, so the transistor Q2 is turned off and the transistor Q4 is turned on. Thus, the transistor Q3 is turned on through the optocoupler chip U5. In this way, the parallel load resistors R21, R23, R25, and R19 (each with a resistance of 1KΩ) act as the load of the PWM control output circuit 4, which increases the pulse width of the PWM (or increases the frequency of the PWM). In this way, the non-control output circuit 5 is stabilized within its rated voltage range. The optocoupler chip U5 plays the role of isolating the two outputs of the PWM control output circuit 4 and the non-control output circuit 5.

[0022] The above embodiments are merely preferred embodiments of the present utility model and are only used to explain the present utility model, not to limit the present utility model. Any changes, substitutions, combinations, simplifications, modifications, etc., made by those skilled in the art without departing from the spirit and principle of the present utility model shall be considered equivalent substitutions and shall be included within the protection scope of the present utility model.

Claims

1. A switching power supply circuit for improving the load-carrying capacity of non-control output circuits, characterized in that: Its circuit structure includes an AC input circuit, an EMI rectifier and filter circuit, a power transformer circuit, a PWM control output circuit, a non-control output circuit, a PWM regulation and control circuit, and a load switching circuit. The output terminal of the AC input circuit is connected to the EMI rectifier and filter circuit. The positive terminal of the output terminal of the EMI rectifier and filter circuit is connected to the positive terminal of the first primary winding of the power transformer T1 in the power transformer circuit. The negative terminal of the first primary winding is connected to the PWM regulation and control circuit. The second primary winding of the power transformer T1 provides the operating voltage to the PWM control chip U1 of the PWM regulation and control circuit. The output of the first secondary winding of the power transformer T1 is connected to the PWM control output circuit, and the output of the second secondary winding of the power transformer T1 is connected to the non-PWM control output circuit. The control output circuit; the output of the PWM control output circuit inputs a feedback signal to the feedback input terminal of the PWM control chip U1 of the PWM adjustment control circuit through the optocoupler chip U4; the non-control output circuit includes a step-down regulator chip U3, the voltage input terminal of which is connected to the output terminal of the second winding of the secondary side of the power transformer T1; the load switching circuit is connected between the PWM control output circuit and the non-control output circuit; the load switching circuit includes transistors Q2, Q3 and Q4, an optocoupler chip U5, and Zener diodes Z1 and Z2; the non-control output circuit... The voltage input terminal of chip U3 is connected to the base of transistor Q2 via series-connected Zener diodes Z1 and Z2 and resistor R38. One path of the collector of transistor Q2 is connected to the positive output terminal Vo2 of the uncontrolled output circuit via resistor R32. The emitter of transistor Q2 is connected to the signal ground SGND2 of the uncontrolled output circuit. The other path of the collector of transistor Q2 is connected to the base of transistor Q4 via diode D1. The emitter of transistor Q4 is connected to the signal ground SGND2. The collector of transistor Q4 is connected to one input terminal of optocoupler chip U5, and the other input terminal of optocoupler chip U5... The positive output terminal Vo2 is connected via resistor R29. One output terminal of optocoupler chip U5 is connected to the positive output terminal Vo1 of the PWM control output circuit via resistor R27. The other output terminal of optocoupler chip U5 is connected to the base of transistor Q3. The emitter of transistor Q3 is connected to the signal ground SGND1 of the PWM control output circuit. A parallel load resistor R21, R23, R25, and R19 are connected between the collector of transistor Q3 and the positive output terminal Vo1. When neither the PWM control output circuit nor the non-control output circuit is connected to a load, Zener diodes Z1 and Z2 are reverse-biased and broken down.

2. The switching power supply circuit for improving the load-carrying capacity of the non-control output circuit according to claim 1, characterized in that: The AC input circuit is equipped with an overcurrent protection fuse F1 and a lightning protection varistor MOV1.

3. The switching power supply circuit for improving the load-carrying capacity of the non-control output circuit according to claim 1, characterized in that: The buck regulator chip U3 is model number PL82051.

4. The switching power supply circuit for improving the load-carrying capacity of the non-control output circuit according to claim 1, characterized in that: The optocoupler chips U4 and U5 are model number EL1019.

5. The switching power supply circuit for improving the load-carrying capacity of the non-control output circuit according to claim 1, characterized in that: The transistors Q2, Q3, and Q4 are 2222 type transistors.

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